Life of silver-surfaced contacts on arcing duty

IN THE ELECTRICAL industry, from the electric range in the home to the protective relay in the generating station, reliable performance of large equipments frequently depends upon the proper functioning of relatively small electric contacts. To aid in the design of one widely used contact configuration, that of a silver-surfacing layer bonded to a backing material, a fundamental investigation has been made of the factors which determine arcing life. Geometric variables include silver thickness, contact diameter, surface curvature, and backing arrangement. Electrical variables include current from 5 to 35 amperes, and voltage from 6 to 440 volts, all at 60 cycles. Kinematic variables include mechanical bouncing and contact velocity.